1. Field of the Invention
The present invention relates to a keyboard apparatus that is suitable for in use applications such as notebook-type personal computers.
2. Description of the Related Art
Portable personal computers generally have a main unit and a key top cover, the main unit having a keyboard which resiliently supports a large number of key tops. The key top cover of the personal computer typically has an LCD display on its reverse side, and is pivotally supported on the main unit to allow it to swing freely.
In a personal computer configured as noted above, when the computer is to be used the closed computer cover is swung into the open position, thereby exposing both the liquid-crystal display and the keyboard to the outside.
When carrying the above-noted computer, the cover of the personal computer is swung into the closed position so that the liquid-crystal display and keyboard are covered, therewith.
In this type of personal computer, to achieve a good key touch at the key tops, each key top is supported on a main unit of the keyboard by an X-shaped pantograph, enabling free rising and falling of the key top.
An example of this type of keyboard that was used in the past is shown in FIG. 4.
In the above-noted type keyboard, the keyboard mechanism 41 of which is shown in FIG. 4, has a keyboard 42 (key base), a key top 43 and a pantograph 44 as well as a resilient member 45.
Onto the key base 42 are placed the same number of contact parts (not shown in the drawing) as there are key tops. The key top 42 has a large number of pantograph pivot point support pairs 46, which support the key base side pivot points (to be described below) of the pantographs 44.
The pantograph pivot point support pair 46 has two pantograph pivot point supports 46a and 46b, which are arranged in a line.
There are a large number of key tops 43, which are each supported on the key base 42 by a pantograph 44, so as to enable free rising and falling, and which are also supported by a resilient member 45. Each key top 43 has a pantograph pivot point link pair 47, which links the key top side pivot points (to be described below) of the pantograph 44.
The pantograph pivot point link pair 47 has pantograph pivot point links 47a and 47b, which correspond to the pantograph pivot point supports 46a and 46b.
This pantograph 44 is an X-shaped pantograph that has two links 48 and 49 to which are linked the link center parts 48a and 49a so as to be able to freely rock to each other, the pantograph being disposed between the key base 42 and each one of the key tops 43 so as to allow free expansion and contraction therebetween.
The ends of the links 48 and 49 each have key base side pivot points 48A and 49A, which correspond to the pantograph pivot point supports 46a and 46b, and key top side pivot points 48B and 49B, which correspond to the pantograph pivot point links 47a and 47b.
The resilient member 45 is made of rubber and includes within it a contact part (not shown in the drawing) which corresponds to a contact part on the key base 42, and is disposed between each of the key tops 43 and the key base 42.
By virtue of this arrangement, when a key top 43 is pressed toward the key base 42, along with this pressing action, the resilient member 45 contracts, so that the contact part within the resilient member 45 comes into physical contact with a contact part on the key base 42. When the pressed condition of the key top 43 is released, the resilient member 45 expands, so the above-noted contact parts move away from each other.
In a keyboard mechanism of the past, however, because the mechanism is one in which the pantograph 44 expands and contracts in response to pressing and releasing a key top 43, when a key top is not in use, it is positioned at the topmost position, by means of the resilient member 45.
As a result, there arises the problem that the height-direction dimension of the key board when the key tops are not in use becomes large.
In the Japanese Unexamined Patent Publication (KOKAI) No. 8-22348, there is a proposal of an "information processing apparatus" which has a large number of key tops that can be supported by rubber springs on a base so as to freely rise and fall, and a balloon, which is disposed between these key tops and the base, and which is linked to a tube for the purpose of supplying and exhausting air.
In this type of keyboard mechanism, because the movement stroke of the keys in the key top height direction is adjusted by means of the air pressure the balloon, the tube to supply air to within the balloon and a valve to open and close the tube are required as a mechanism for adjustment of the key top height, this making the key top height adjustment mechanism complex.
In the Japanese Unexamined Patent Publication (KOKAI) No. 5-290673, there is a disclosure of prior art directed at a "keyboard apparatus" that has a guiding support member that guides and supports a pantograph in the up and down direction, and in the Japanese Unexamined Patent Publication (KOKAI) No. 5-298000, there is disclosure of prior art directed at a "keyboard apparatus" that has a cover that has a sliding groove which guides the up and down movement of a sheet member.
In the above-noted example of prior art, the adjustment of the movement stroke of the keys in the key top direction in the former case (Japanese Unexamined Patent Publication (KOKAI) No. 5-290673) is that of moving a pantograph pivot point in a straight line direction, and in the latter case is that of performing this adjustment by moving inside of a cam groove, so that there is no change in the front-to-back movement of the key top, this causing the problem of poor visibility of the marking on the key top.
On the other hand, in the Japanese Unexamined Patent Publication (KOKAI) No. 61-80718, although a key board used for electric devices is disclosed, it only shows a thin film key board without using a plurality of independent key tops but with a plurality of resilient plates each forming a respective switching means.
And the switching means of this Publication further is provided with a movable spacer which is caused to be moved in synchronization with a sliding motion of a power switching means so that when the power switching means is turned on, the movable spacer is moved so as to rise up the resilient plates whereby a projected portion will be created on a surface of the thin film.
On the other hand, when the power switch is turned off, the resilient plates are moved oppositely so as to retract the projected portion from the surface of the thin film.
Therefore, this publication does not show a key board having a configuration in that a height of each one of the key tops can be changed in response to the movement of the key top cover.
Further, in the Japanese Unexamined Patent Publication (KOKAI) No. 6-36649, although a key board provided with a plurality of key-tops each having a pantograph mechanism, the height of each of the key-top of the publication is fixed and thus it cannot be changed in synchronization with a movement of a key top cover.
Accordingly, in consideration of the above-noted problems accompanying the prior art, it is an object of the present invention to provide a keyboard mechanism which, by causing the pivot at one side of the pantograph to move with a swinging motion so as to apart from a surface of a key base, enables a reduction of the size of the keyboard in the height direction while simplifying the mechanism for adjusting the key top height, and also achieves good visibility of the marking on the key top.